Discharge device with connector of low thermal and high electrical conductivity



March 29, 1949. HA. VAN MEURS 2,

DISCHARGE DEVICE WITH CONNECTOR OF LOW THERMAL AND HIGH ELECTRICALCONDUCTIVITY Filed July 20, 1946 AGE/VT Patented Mar. 29, 1949 DISCHARGEDEVICE WITH CONNECTOR F LOW THERMAL AND HIGH ELECTRICAL CONDUCTIVITYHubertus Anthonius van Meurs, Eindhoven, Netherlands, assi'gnor toHartford National Bank and Trust Cpmpany, Hartford, Conn.,

as trustee Application .Iuly 20, 1946, Serial No. 685,177 In theNetherlands June 15, 1945 Section 1, Public Law 690, August 8, 1946Patent expires June 15, 1965 4 Claims. 1

This invention relates to an electric discharge tube, the electrodesystem of which is su ported substantially by one or more supportingrods which are sealed into the wall of the tube and outside the tubehave the shape of contact pins. It more particularly relates to thestructure of such supporting rods.

There is a general aim to give discharge tubes as small a height aspossible. This means that the length of the supporting rods which islocated between the electrode system and the place of sealing must be assmall as possible. If the supporting rods are sealed into the Wall ofthe tube and outside the tube have the shape of contact plus, there aresoon dimculties, however, since such supporting rods must have a fairlylarge thickness, due to which heat is transmitted from the electrodes tothe contact pins. Especially in tubes that are highly loaded the pinsmay thus become so hot as to oxydise resulting in 'poor contact in thetube holder and consequently in further production of heat anddisturbances, in the course of which even burning of the contact springsand deterioration of the seal may arise.

Several means were already suggested for preventing the transmission ofheat by cathodes. Thus it was known to provide indirectly heatedcathodes with sleeves of poorly conductive material, due to which thetransmission of heat "to the points of support is reduced.

Furthermore it is known to avoid undue transmission of heat from adirectly-heated cathode to the supply-wires by forming a certain numberof circumferential roovesin the supporting rods. In order to obviate asmuch as possible the attenuation of the rods resulting from thesegrooves, little tubes of insulating material are slipped over thegrooves. Furthermore it was known to provide for the same purposethinwalled little tubes of resistance material between the currentsupply wires and the extremities of the filament of an indirectly heatedcathode. In order to reduce the heat emission losses of these littletubes, they could be gilt, copper-plated or silver-plated. In thesetubes, however, a Joule production of heat must occur which is equal tothe thermal losses resulting from the transmission. Consequently, thetubes must have a fairly high electric resistance. In all theseconstructions, however, the drawback arises, that, owing to these means,either the electric resistance is also increased, or besides themechanical strength is greatly reduced. These constructions need not,however, withstand any great forces, since they serve only to support afilament. The requiremen'ts which a supporting rod has to satisfy areentirely different if it has to serve for the heavier electrodes or forthe whole of the electrodes system and, in addition, fulfills thefunction of a supply conductor. In this case it is not possible withoutany further expedients to utilise one of the above mentioned known meanswithout involving great drawbacks in connection with either themechanical strength, or the electrical resistance.

Now, according to the invention, in an electric discharge tubecomprising an electrode system carried substantially by at least onesupporting rod which is sealed into the wall of the tube and V whichoutside the tube has the shape of a contact pin, that portion of thesupporting rod which is located between the system and the place ofsealing has such a shape that the transmission of heat alon the rod isreduced at least so strongly as to avoid any oxydation of the portion ofthe supporting rod protruding from the tube, whilst the electricalresistance for the operating currents of the tube and the mechanicalstrength of the rod are substantially unvaried.

It is thus possible for the distance between the electrode system andthe place of sealing to be given a comparatively short length withoutdifilculties being involved during the deprivation of gases of theelectrodes or in operation, even in tubes with electrodes that areloaded very highly and which may therefore acquire a high temperature inoperation.

The invention is particularly advantageous for tubes having a plane baseinto which the supply wires which outside the bulb have the shape ofcontact pins are sealed. In this case the invention is only applied tothose supply conductors which serve at the same time as supporting rodsfor the electrode system. The other supply wires are connected in knownmanner to the electrode supports by means of a flexible connecting pieceof fairly great length. Consequently these conductors cannot reallycontribute to a rigid support of the electrode system.

In order that the invention may be clearly understood and readilycarried into effect, it will be described more fully with reference tothe accompanying drawing.

In the figure reference numeral l denotes the electrode system of atransmitting tube housed in a bulb 2 and fixed to a base 3. Contact pinsare sealed into the base 3, pin 4 inside the tube changing into asupporting rod 4, 4", which substantially carries the system I. Thedistance between the system and the bottom of the tube is comparativelysmall so that there would be a risk of contact pin 4 being overheated ifthe supporting rod 4' would extend in a straight line, Especially indegassing the tube, during which treatment the electrodes acquire a hightemperature, this risk would be great, as well as the danger of crackingof the bottom of the tube whilst furthermore, due to the prolongedheating during the operation of the tube, there is in this case the riskof oxidation with all consequences involved. Now, according to theinvention, the supporting rod 4' is interrupted at 5, the two parts 4',4" being electrically connected by means of a metal strip 6. In order tokeep down the electrical and more particularly the high-frequencyresistance of the strip, it is made either from copper or silver, orfrom resistance material which is copperplated or silver-plated, due towhich especially the high-frequency resistance as a result of the skineffect need not be higher in practice than it would be if the rod 4' 4"would extend in a straight line. Consequently in tubes in which thesupporting rod concerned must convey great high-frequency currents, usewill preferably be made of a strip of nickel-iron which is copperplatedor silver-plated, since the heat conduction is in this case smaller thanit is with a strip of the same size which is made from copper or silver.In tubes for low-frequency amplification, however, use is preferablymade of a strip of copper or silver. A low electrical resistance of thestrip is also of importance in view of the Joule heat produced in thestrip, by which the efiect of the decrease of the heat transmissionwould for the greater part be neutralised. With high-frequency operatingcurrents the essential point therefore is a good conductivity of thesurface of the strip. The strip 6 can withstand only a certain stress,but the support proper of system I is effected by means of U-shapedclasp I, the two limbs of which are secured in an insulating centreingbody of the electrode system and the middle of which is welded to thepart 4' of the supporting rod 4', 4". Owing to the fact that the claspis only connected to the electrode system by means of insulatingmaterial, the heat transmission through this clasp is small. If desired,the system maybe supported by further supporting pins to which theinvention is applied. The other pins II] are connected to the electrodesupports by means of long thin conductors 9 and cannot thereforecontribute to an appreciable extent to the support proper of the system.

The clasp I may be secured in the insulating body by means of littlerings welded on it, so that any shift along this clasp is avoided. Ifdesired, the strip 6 may be of copper, in which event it is advantageousto place it in a curvature so that its heat emission is increased andits heat transmission is decreased and, even if the whole of the stripconsists of copper, no overheating of the lead-through of the contactpins can occur. If the strip has to withstand a certain stress or mustconvey strong high-frequency currents, it will preferably be made fromresistance material 4 such material is stronger than copper or silver.

It is evident that still further embodiments according to the inventionare possible.

What I claim is:

1. An electric discharge device comprising an envelope, electrodeswithin said envelope, an insulating body secured to and supportin one ofsaid electrodes, a member secured to and supporting said insulatingbody, an electrically conductive pin extending through and sealed tosaid envelope and being secured to and supporting said member, and aconnector of high electrical conductivity and low thermal conductivityelectrically interconnecting said pin and said one electrode.

2. An electric discharge device comprising an envelope, electrodeswithin said envelope, an insulating body secured to and supportin one ofsaid electrodes, a member secured to and supporting said insulatingbody, an electrically conductive pin extending through and sealed tosaid envelope and being secured to and supporting said member, and aconnector of low thermal conductivity plated with a metal of highelectrical conductivity electrically interconnecting said pin and saidone electrode.

3. An electric discharge device comprising an envelope, electrodeswithin said envelope, an insulating body secured to and supporting Oneof said electrodes, a U-shaped member supporting said insulating memberand secured thereto at the ends of the legs of the U-shaped member, anelectrically conductive pin extending through and sealed to saidenvelope and supporting said U- shaped member and secured thereto at thecurved portion thereof by a weld, and a connector of low thermalconductivity plated with a metal of high electrical conductivityelectrically interconnecting said pin and said one electrode.

4. An electric discharge device comprising an envelope, electrodeswithin said envelope, an insaid insulating member and secured thereto atwhich is silver-plated or copper-plated, since the ends of the legs ofthe U-shaped member, an

electrically conductive pin extending through and sealed to saidenvelope and supporting said u shaped member and secured thereto at thecurved portion thereof by a weld, and a connector of low thermalconductivity plated with a metal of high electrical conductivityelectrically connected to said pin at said weld and electricallyconnected to said one electrode.

HUBERTUS ANTHONIUSvAN MEURS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,197,615 Eldred Sept. 12, 19162,244,358 Ewald June 3, 1941 2,355,083 Krim Aug. 8, 1944 2,380,496 BeardJuly 31, 1945

